Most conventional x-rays are taken using a sheet of radiographic film retained within a cassette that includes an intensifying screen to convert the x-radiation to visible light. After exposure, the film is removed and processed and the cassette is reused. Where large numbers of x-rays are taken, it is desirable to label the film itself with patient information. For this purpose, many x-ray cassettes include a patient identification window. Typically, this feature consists of an opening covered by a light-tight movable shutter. In use, the cassette is placed in a specialized patient identification camera which establishes a light-tight seal against the cassette surrounding the window. The shutter is opened, patient identification information is transferred onto the x-ray film contained within the cassette using visible light, and the shutter is closed. When the shutter is position it is typically retained in place by a latching member or catch. Mechanical and magnetic latching members have been used.
U.S. Pat. Nos. 4,313,538 and 4,972,450 teach cassettes including patient identification windows. In both of these patents, the patient identification camera has a pin that moves through a hole in a hatch or slideable member to release a mechanical latching member or catch. The hatch or slideable member is slid open and closed using the same pin. The latching member or catch is resiliently biased and automatically re-engages when the pin is retracted after exposure of the film. A patient identification camera including such a pin mechanism is convenient; however, there is a shortcoming that the hatch or slideable member has an aperture extending through it and the latching mechanism must therefore also act as part of the light barrier. Parts of the light barrier require close tolerances and are subject to scuffing as the pin moves through the aperture and pivots the latching mechanism.
It would therefore be very desirable to be able to provide an x-ray cassette which has an aperture free shutter and a latching mechanism that is not part of the light barrier.